1. Field of the Invention
The present invention relates to image processing technology for displaying images, in accordance with image signals of an interlace method, by a non-interlace method.
2. Description of Related Art
For video signals used for displaying an image in television and video, a commonly called interlace method is employed. In the interlace method, an image for one screen, including a plurality of horizontal lines, is divided into odd-numbered lines and even-numbered lines which are displayed alternately on the screen. An image including all the odd-numbered. lines and the even-numbered lines is called a xe2x80x9cframexe2x80x9d, while an image represented by the odd-numbered lines and an image represented by the even-numbered lines are called an xe2x80x9codd-numbered fieldxe2x80x9d and an xe2x80x9ceven-numbered fieldxe2x80x9d, respectively.
Since cathode-ray tubes chiefly used in television and video have a relatively long after-image time, even if the odd-numbered lines and the even-numbered lines are alternately displayed by the interlace method, flickering of images is not noticed much. In contrast, since a liquid-crystal panel has a relatively short after-image time, if an image is displayed by the interlace method, the image appears to flicker. Consequently, in the liquid-crystal panel, a non-interlace method is employed for supplying an image signal to all the lines of the liquid-crystal panel each time. When an image is to be displayed in the liquid-crystal panel in accordance with an interlaced video signal, the interlaced video signal is converted into a non-interlaced display image signal and supplied to the liquid-crystal panel.
FIGS. 14(A), 14(B), and 14(C) are illustrations showing an example in which an interlaced video signal is displayed in a liquid-crystal panel (LCD panel) by a non-interlace method. An original image shown in FIG. 14(A) has 100 horizontal lines. At this time, when an odd-numbered field image is displayed in the liquid-crystal panel by the non-interlace method, as shown in FIG. 14(B), line data L1, L3, L5, L7, and L9 of the odd-numbered lines of the original image are provided to each of the five lines of the liquid-crystal panel. The letter and numeral xe2x80x9cL1xe2x80x9d indicates the image data of the first line of the original image. On the other hand, when an even-numbered field image is displayed in the liquid-crystal panel, as shown in FIG. 14(C), line data L2, L4, L6, L8, and L10 of the even-numbered lines of the original image are provided to each of the five lines of the liquid-crystal panel. As a comparison between FIG. 14(B) and FIG. 14(C) shows, the line positions in the original image of the line data of the odd-numbered fields and the even-numbered fields provided to the same lines of the liquid-crystal panel differ. For this reason, flicker occurs in the displayed image.
In this specification, the size of the image displayed, with the lines of each field being arranged without a clearance, as in FIGS. 14(B) and 14(C), is called an xe2x80x9cinitial sizexe2x80x9d. Therefore, the width in the vertical direction at the initial size of the displayed image is one half that of the original image, and the width in the horizontal direction is equal to that of the original image. The magnification of the display image is assumed to be calculated by using this initial size as a reference.
FIGS. 15(A) and 15(B) are illustrations showing an example in which the image is enlarged three times in the vertical direction when the interlaced video signal shown in FIG. 14(A) is displayed in the liquid-crystal panel by the non-interlace method. The image data representing the lines added by enlargement is created by straight-line interpolation of the image data of the original lines of each field. As can be seen from a comparison between FIGS. 15(A) and 15(B), the line positions in the original image of the line data of the odd-numbered fields and the even-numbered fields provided to the same lines of the liquid-crystal panel differ. Therefore, also in this case, flicker occurs in the displayed image.
As described above, conventionally, since the line positions in the original image of the image signal provided to the same line of the liquid-crystal panel deviate between the odd-numbered fields and the even-numbered fields, a problem arises in that flicker occurs in the displayed image. Such a problem is not limited to a case in which a liquid-crystal panel is used, but broadly, is a problem common to a case in which an interlaced image signal is converted into a non-interlaced one and displayed at a desired magnification.
This invention has been achieved to solve the above-described problems of the conventional technology. An object of the present invention is to provide technology which is capable of reducing flicker when an interlaced image signal is converted into a non-interlaced one and displayed at a desired magnification.
The above-described problems are solved by the image processing method, the image processing apparatus, and the image display apparatus described below.
The image processing method of the present invention is an image processing method for supplying, by a non-interlace method, image signals to a light modulation section in accordance with two field image signals for displaying the odd-numbered line fields and the even-numbered line fields of an original image by an interlace method, the image processing method comprising the steps of:
generating two image signals for display to be alternately provided to the light modulation section from the two field image signals, respectively, in order to alternately supply, by a non-interlace method, the image signals representing the two images, in which two field images represented by the two field image signals are each enlarged a times in the vertical direction, to the light modulation section; and generating the two image signals for display by performing interpolation of at least one of the two field image signals so that each pair of signals among the signals of each line of the two image signals for display, which are alternately provided to the same line of the light modulation section, indicate the image at mutually equal line positions defined within said original image.
Here, the xe2x80x9clight modulation sectionxe2x80x9d refers to an apparatus for generating light from which an image in accordance with an image signal can be visually recognized. As the light modulation section, for example, various apparatuses, such as a liquid-crystal panel, a plasma display panel, and a CRT, may be used.
According to the image processing method of the present invention, two image signals for display which are alternately provided to the same line of the light modulation section represent an image at mutually equal line positions defined within the original image. Therefore, there is no occurrence of the two field images supplied to the light modulation section being deviated from each other in the vertical direction. This makes it possible to prevent an occurrence of flicker when an image signal representing an enlarged/reduced image in the vertical direction in accordance with an interlaced image signal is supplied to the light modulation section by a non-interlace method.
In the above-described image processing method, when the two field images are further enlarged b times in the horizontal direction, an image signal representing a target pixel, which is a pixel on each line of the light modulation section, is generated by performing interpolation of image signals of four pixels contained in the odd-numbered line fields and in the even-numbered line fields in the original image, respectively, in the odd-numbered line fields and the even-numbered line fields, and as the four pixels, the closest four pixels which surround the target pixel in a lattice form may be selected.
According to the above-described method, it is possible to provide image data at the same pixel position within the original image to the same pixels of the light modulation section in either the odd-numbered line fields or the even-numbered line fields. As a result, when image signals representing an image which is enlarged/reduced at a desired magnification in the vertical direction and in the horizontal direction in accordance with an interlaced image signal are supplied to the light modulation section by a non-interlace method, occurrence of flicker can be prevented.
The image display apparatus of the present invention is an image display apparatus for supplying, by a non-interlace method, image signals to a light modulation section in accordance with two field image signals for displaying the odd-numbered line fields and the even-numbered line fields of an original image by an interlace method, the image display apparatus comprising:
an image processing section, in order to alternately supply, by a non-interlace method, image signals representing two images, in which two field images represented by the two field image signals are each enlarged a times in the vertical direction to the light modulation section, for generating two image signals for display to be alternately provided to the light modulation section from the two field image signals, respectively, and for generating the two image signals for display by performing interpolation of at least one of the two field image signals so that the two image signals for display generated based on the respective two field image signals, which are alternately provided to the same line of said light modulation section, indicate the image at mutually equal line positions defined within said original image.
When the two field images are each enlarged b times in the horizontal direction, the image processing section may generate an image signal representing a target pixel, which is a pixel on each line of the light modulation section by interpolating the respective four pixels contained in the odd-numbered line fields and the even-numbered line fields in the original image, respectively, in the odd-numbered line fields and in the even-numbered line fields, and as the four pixels, the four closest pixels which surround the target pixel in a lattice form may be selected.
According to the above-described image display apparatus, similarly to the above-described image processing method, when image signals representing an image which is enlarged/reduced in accordance with interlaced image signals are supplied to the light modulation section by a non-interlace method, occurrence of flicker can be prevented.